1. Field of the Invention
The present invention relates to a rear suspension system for a wheeled vehicle and more particularly to a suspension system for a motor-tricycle having a pair of rear wheels.
2. Description of the Prior Art
In a motor-tricycle having a pair of wheels mounted on opposite ends of a rear axle, the two rear wheels generally run at the same speed, even when making a turn at a curve, because such a tricycle usually has no differential gear. Hence, when turning a curve, it is conventional for a rider to shift his weight far enough so as to cause either one of the rear wheels to either lift off or slip on the surface of a road. For that purpose, the machine should preferably be designed to respond readily to a rider shifting his weight while enabling him to keep a stable riding position particularly when making a turn, as a curve, for example.
However, a conventional rear suspension system used in such a tricycle has hitherto had a swing arm which carries a rear axle at its rear end. The front end of the swing arm, is pivotally coupled to a frame. The arm must be wide enough so that the frame and the swing arm tilt or bank as a single unit, in either the right or the left direction, when viewed in the direction in which the machine runs. To be more specific, the swing arm is enabled to swing up and down relatively to the frame, but is not allowed to tilt or twist freely in the right or left direction, relatively to the frame. As a result, it is difficult for a rider to seize an opportunity for shifting his weight when making a turn, since it is difficult for him to tilt the frame, prior to shifting his weight, relatively to the swing arm. Further, when one of the rear wheels encounters holes or bumps on a road during the turn, the frame may tilt greatly in either the right or the left direction, so that it becomes difficult for the rider to shift his weight and to turn the curve while maintaining a stable riding position.
Furthermore, a hot exhaust silencer or muffler is positioned outside the swing arm in the conventional system, therfore it is possible that the silencer may make contact with either a combustible material on a road surface or a rider's body.